The present invention relates to the field of the treatment of the exhaust gases of an internal combustion engine, for example of a motor vehicle. The internal combustion engine may be a lean-burn engine, particularly a diesel or gasoline engine.
More particularly, the invention relates to the field of checking the operating state of a catalytic converter with which the exhaust line is provided.
Internal combustion engines produce exhaust gases which contain polluting substances such as oxides of nitrogen, unburned hydrocarbons and carbon monoxide, that have to be treated before the gases are released into the atmosphere.
Motor vehicles are often fitted with a catalytic converter arranged in the exhaust line of the engine, able to oxidize the carbon monoxide and the unburned hydrocarbons.
Motor vehicles are also generally fitted with a device for checking the operating state of the catalytic converter, making it possible to check that the catalytic converter is operating correctly and alert the driver to any malfunction.
Of the causes of malfunctions, ageing of the catalytic converter leads to a drop in the efficiency with which the unburned hydrocarbons and the carbon monoxide are converted into water and carbon dioxide, this drop being due, amongst other things to a reduction in the active surface area for the treatment of the pollutants in the catalytic converter. This then results in an increase in the light-off temperature for the oxidation reactions, particularly in the temperature above which the conversion efficiency is greater than or equal to 50%.
Document EP-1 323 905 (RENAULT) proposes a method of checking the operating state of a catalytic converter of an exhaust line of an internal combustion engine with the converter energized by injecting fuel and checking the value of a variable representative of the amount of heat given off by an oxidation reaction within the catalytic converter, by monitoring the operating temperature of the catalytic converter and injecting fuel at a temperature corresponding to a light-off temperature of a catalytic converter that is operating correctly.